This invention relates to an apparatus or dancer for establishing a plurality of operating tensions in a moving web, and more particularly, to a dancer assembly in which the dancer roller support structure is mounted in a cantilevered fashion.
Generally, dancers are well-known to the art of controlling a moving, high-speed web such as paper. In a typical installation, a dancer is used in association with two idler rollers which are mounted for rotation about parallel axes. The dancer includes a dancer roller mounted on a support structure for rotation about an axis parallel to the rotational axes of the idler rollers. The support structure is mounted for pivoting about another axis parallel to the axes of the idler rollers. The web is passed across one idler roller, around the dancer roller, across the other idler roller and into web consuming or processing equipment. As the surface velocity of the unwinding roll increases and decreases relative to the velocity of the web processing equipment, the support structure pivots the dancer roller toward and away from the idler rollers, and the rotational velocity of the dancer roller increases and decreases. As a result, a constant operating tension, pre-selected for the type of web material and the type of web processing equipment, is established.
A problem inherent in dancer assemblies as described is wrinkling of the web. That is, the rotational axis of the dancer roller must be kept substantially parallel to the axes of the idler rollers, or the web material will develop axial stresses, causing the web to fail in the lateral, or cross-web, direction, and overlap itself. To avoid this problem, in the past, dancer assemblies have been disclosed in which the dancer roller, as well as the support structure and the idler rollers, are mounted on laterally spaced bearings. Fixed axes for rotation are thus established, and precise positioning of the bearings results, ideally, in parallel axes for all the equipment.